Copper fungicidal compositions safened with zinc sulfite



fact that it furnishes a suicient concentration of zinc ion to exert a substantial buffering effeet. When copper fungicides are used together with organic fungicides or insecticides, the effectiveness of zinc sulphite is further attributed to the antagonistic action of the zinc ion against the copper ion. It seems that the zinc ion more readily reacts with Vthe organic fungicides or insecticides and thus protects against interaction of the copper ion.

This protective action of zinc sulphite is highly beneficial in protecting plants against fungus disease when both organic .and copper fungicides are needed, because it is possible to use both in one application if zinc sulphite is also used. For the control of, say, anthracnose on tomatoes, the organic fungicides, e. g. disodium ethylene bisdithio-carbamate, are essential. For the control of, say blight, it is necessary to use copper fungicides. Since these two materials are not compatible, it has previously been necessary to spray or dust them separately with definite intervals between applications, say ten days, to avoid copper injury and to obtain effective fungicidal .'actiOn. The chief drawback of' this system is that'the regular interval of ten days between the applications makes the interval between copper applications twenty days, a period too long to control blight successfully. On the other hand, if the interval; between alternate copper and orlganic applications is cut to ve days so as to reduce the interval between copper applications to ten days, six treatments 'per month are required so that the amount of labor required is frequently beyond the ability of the farmer to provide and in any event its cost is excessive. This ,drawback can be overcome by a single application every ten days using copper and organics in the same spray or dust application in the presence of Zinc sulphite. Moreover, when the copper and'organic fungicides are applied alternately' 'the period between the applications is not denitely established but depends upon'the experience of the grower. Also this period is purely experimental since it depends upon atmospheric conditions which govern the rate at which fungus infection spreads.

Therefore, it isv seen Vthat an expert is required if fthese'fungicides are used alternately. Furthermore; it is difcult for the farmer to maintain the proper regular sequence of and interval A*between :frequent alternate applications, because of other demands on the available time and labor,

While any farmer can apply the combination in `the presence oil zinc sulphite.

It is emphasized that one of the chief advan- -tages of zinc sulphite is that it is a complete product as a buffering Asubstance and does not require the 'additionjof' alkaline materials such as limelas is thecase with other soluble zinc salts.' It has been found that in most cases alkaline materials have an adverse effect on both organic and copper fungicides. The chief disadvantages in using alkaline materials such as decompose the organic insecticides, such as pyref1thrumrotenone or nicotine products which may be used in the same application. For example, when an attempt was made to neutralize soluble zinc salts with strong alkalies such as sodium or potassium hydroxide, it was found that the so` brown color of cupric oxide.

as zinc phosphate and zinc oxalate) in order to furnish zinc ion, but these acids also exert an excessive dissolvingA action on the copper fungicides.

Arsenicals may also cause injury to the plant. That is, arsenicals such as lead arsenate, calcium arsenate, etc., which are used for insecticdal purposes are relatively insoluble, but injury to the plant may result from soluble fractions liberated on exposure to the atmosphere- The use of zinc sulphite greatly reduces such injurious effects of arsenicals. Its effectiveness in this respect is again attributable to its buffering action as in the case of copper ungicides.

The effectiveness of zinc sulphite in protecting plants against both copper and arsenical injuries can be further explained as follows. As stated above, soluble zinc salts such as zinc sulphate can not be used because of severe injury to fruit and foliage. On the other hand, basic Zinc salts such as obtained by the combination of zinc sulphate and lime are ineffective to prevent arsenical or copper injuries because soluble zinc is obtained only as a result of carbonation. High calicum lime which is commonly used for this purpose does not carbonatebefore ve or six days under ordinary atmospheric conditions, and carbonation will simultaneously cause increased solubility in arsenicals or coppers. Arsenical or copper injuries due to the formation of soluble arsenic or copper usually occur much ahead of the liberation of zinc ion from basic zinc sulphate. Thus soluble zinc secured from basic zinc' salts does not give the desired protection in man3 cases, whereas zinc sulphite is much more effective as explained above.

Moreover, when insoluble copper fungicides such as basic copper sulphate are used in combination with arsenicals there is an undesirable interaction between copper and arsenical that reduces the eiectiveness of the copper. Zinc sulphite in this case has a two-fold action:

(a) The zinc ion reduces arsenical injury.

(b) The zinc ion protects the copper ion against interaction with soluble arsenicals and thus renders the copper more effective as a fungicide. This increased effectiveness of the insoluble copper fungicides is highly valuable since in many cases these copper fungicides have proved to be lacking in fungicidal efficiency when used in combination with arsenicals.

Thus in dust mixtures containing-both copper fungicides and arsenical insecticides, zinc sulphate can not be used without lime because of injury to the plant, and the use of lime with zinc sulphate causes destabilization of the insoluble copper fungicides. Such dust mixtures are often kept in storage for a considerable period during which the fungicidal efficiency of the copper fungicide is greatly reduced by the action of the lime. Zinc sulphite, however, can be readily used in such a dust mixture without any lime. Inthis u case zinc ion reduces the arsenical injury on one hand, and renders copper more effective on the other hand by protecting the copper ion against interaction With `arsenical residue.

`A further beneficial use of zinc sulphite found to be with copper dust mixtures containing organic insecticides such as ,pyrethrum rotenone, and nicotine lay-products.. All of these organic insecticides have a tendency to .be destabilized Vby the liberated copper ion which. they readily absorb; when, however, zinc sulphite is used, the zinc ion is more readily absorbed and.

the absorption of the copper ion is reduced, thus minimizing destabilizing effect and loss of effectiveness of these insecticides.

The insoluble copper fungicides in many cases require the use of supplementary materials such as Wheat flour or soya flour or some other materials containing protein, fatty acids, or both to increase adherence. Some 4interaction between copper fungicides and protein, or copper fungi cides and fatty acids may take place so as to ree duce the efficiency of the copper fungicideseven though the resultant copper proteinate or copper soap gives better adherence. It has been found that, in this case, vzinc sulphite has a buffering action with the fatty-acid and protein compounds and helps to maintain the concentration of copper ion unchanged. This probably can be attributed to the fact that zinc ion reacts more readily with the above materials than the copper ion.v

It is a well-known fact that copper fungicides may cause severe injury to fruit (apples, cherries, etc-.l during electrical disturbances as a result of the ammonia and oxides of nitrogen formed in the air. When zinc sulphite is used with the copper fungicides, however, this injurious elfect is minimized because of the buffering action of the zinc ion.

Cuprous oxide shows great killing power of spores in the laboratory, and yetin many cases hasbeen found almost ineffective in the field. This change in fungicidal efliciency is Vprobably attributable to the oxidation of cuprous into cuprie oxide which actuallyv can be observed by the change of color vfrom red cuprous to ydark brown cupric oxide. In this case zinc sulphite acts as van. antioxidant and helps to protect the cuprous oxide against oxidation to cupric oxide.

The protective action of 'zinc sulphite 'against copper injuries and arsenical injuries as mentioned above is highly effective. However, the zinc sulphitey has a tendency to oxidze vto zinc sulphate, decreasing the amount of zinc sulphite available for protective action, and forming increasing amounts of zinc sulphate, which in turn increase'sf'the solubility of copper fungicides and arsenicals. rIhe soluble zinc sulphate itself and the soluble copper and/or arsenical as wel are injurious to fruit and foliage, and the injury may become severe when the Zinc sulphite is exposed to `atmospheric action for considerable periods or when the composition is held in storage as mentioned above. In such `cases theprotective action ofthe 'zinc's'ulphite may be prolonged by the use of "aluminum oxide or iron oxide which greatly diminishes the oxidation of zinc sulphite to zinc sulphate and minimizes the injuries to fruit and foliage.

It should be noted that the aluminum oxide or iron oxide when used alone, i. e., without zinc sulphite, does not have beneficial value in relation to copper or arsenical injuries. Its value lies in prolonging the effectiveness of the zinc sulphite by minimizing its tendency to oxidize to zinc sulphate, This protectiye actlonof aluminum oxidlei.v

iron oxide, or a mixture of :these two substances is most likely due to a buffering action,v since aluminum oxide or iron oxide has a neutral re-U sulphite after application to the plant and espe cially when the :composition stored for long` periods before use.

The use of aluminum salts such as aluminum sulphate together with lime is well known. A1111-,` minum. salt requires the addition of alkaline ma.

terials such as lime, .and the use of aluminumv sulphate plus lime will not give any improvement over zinc sulphate and 'lime as discussed above. Furthermore, it is emphasized thatl zinc sulphite protects the most unstable copper fungicides, such as cuprous oxide, from conversion into` cu pric oxide, an effect which has not been observed in the case of any of the aluminum salts when used alone.

summarizing, it appears that zinc sulphite isA benecial per se to plant growth and as a protection against pests, that it aids in maintaining the effectiveness of fungicides and insecticides, and that it renders very valuable protection of fruits and foliage in the following respects:

(1) Against copper injury `as a result of the dissolving acticn on copper fungicidas of-(a) atmospheric acids, (b) excessive amount of acids secreted by pathogenic fungi,

(2) Against arsenical injury.v A.

(3) Against reaction of copper fungicides with organic fungicides which would otherwise liber` ate soluble copper ions.

(4) Against injury caused by theuse of copper lfungicides and lime-sulphur mixtures.

(Note: These materials cause severe injury not.

only if applied as one spray, but also if applied alternately.) J

(5) Against injury in the case of young apples which are very sensitive to copper injury.'

(6) Against'reaction of copper funglcides with?" protein and fatty acids, which may be used as supplementary materials in the mixture. AIn this case there are two functions of zinc'sul,

phite: (l) to protect against copper injury, (2i` to improve adherence of spray residue on fruit` A and foliage.

The amount of zinc sulphite to be used may' It depends mainly on thel4 amount of copper fungicide or arsenical, or on" vary considerably.

the amount of both when used in combinationl but will vary according to the type of"copp.e'rl and/or arsenical compound used, the character of the inert diluents used in the-dust or spray, and also the type of plant on which the dust or.A spray mixture is used. Furthermore it will be understood that the extent of protective action obtained increases progressively as the amount of zinc sulphite increases up to a maximum'` amount beyond which no further' increase of ethylene bis-dithio-carbamate, lt is common practice to use zinc salt with this fungicide and therefore the amount of zinc sulphite. may be above 60%. When aluminum oxide is used to prolong the protective action of the Zinc sulphite, the ratio of oxide to zinc sulphite may also vary within wide limits. However, it will usually be undesirable for this ratio to exceed 1:4, as increases in the proportion of oxide beyond this ratio will not increase the protection afforded the zinc sulphite. The proportion of oxide may be decreased to as little as 1:14 and substantial benefit still obtained. The corresponding ratios in the case of iron oxide will depend on the composition of the oxide used. For example, in the case of iron oxide consisting of about one-third ferrous oxide and two-thirds ferrie oxide, the ratio should be approximately the same as in the case of aluminum oxide. Y 'The following are examples of suitable cornpositions which may be used with talc, clay or the like as diluents. It will be understood that when the oxide is not desired, it will simply be omitted.

(l) 3 lbs. basic copper sulphate 1 lb. zinc sulphite 0.25 lb. aluminum oxide (2) 1.5 lbs. basic copper sulphate 0.5 1b. disodium ethylene bis-dithio-carcil" It will be understood that the invention is not limited to the particular fungicides and insecticides named above. Thus in addition to basic copper sulphate, basic copper chloride and cupi-ous oxide, other copper fungicides may be used, such as basic copper oxalate and copperalumino silicate. Similarly there may be used other organic fungicides such as ferrie dimethyl dithiocarbamate, ethyl mercury phosphate and other organic insecticidessuch as dichloro-diphenyl-trichlorethane. The useful inorganic insecticides include, in addition to arsenicals, scdium fluoaluminate. These additional materials may be used in compositions conforming to the foregoing description and examples.

In most cases it will be desirable to mix the zinc sulphite with .the other ingredients of the composition so that all may be applied to the plant simultaneously in a single dusting or spraying operation. It is possible, however, to apply the zinc sulphite to the plant separately.

8 In this case the zinc sulphite application ray either precede or follow the copper or arsenical application but the two applications should be made substantially simultaneously; i. e., no more than one or two days should be permitted to intervene if the above mentioned benefits of conjoint use are to be obtained.

It will also be understood that the proportions of the above examples are only illustrative and may vary widely under dierent conditions. Hence reference should be had to the appended claims for a definition of the limits of the in- Vention.

What is claimed is:

1. A composition for application to plant foliage and fruit for the control of pests which contains zinc sulphite together with a copper fungicide.

2. A composition for application to plant foliage and fruit for the control of pests which contains zinc sulphite together with a copper fungicide and an organic fungicide.

3. A composition for application to plant foliage and fruit for the control of pests which contains zinc sulphite together with a copper fungicide and an organic insecticide.

4. A composition for application to plant foliage and fruit for the control of pests which contains zinc sulphite together with a copper fungieide and an arsenical insecticide.

5. A composition for application to plant foliage and fruit for the control of pests which contains zinc sulphite and a protective oxide selected from the group consisting of aluminum and iron oxides together with a copper fungicide.

6. A composition for application to plant foliage and fruit for the control of pests which contains zinc sulphite and a protective oxide selected from the group consisting of aluminum and iron oxides together with a copper fungicide and an organic fungicide.

7. A composition for application to plant foliage and fruit for the control of pests which contains zinc sulphite and a protective oxide selected from the group consisting of aluminum and iron oxides together with a copper fungicide and an organic insecticide.

8. A composition for application to Vplant foliage and fruit for the control of pests which contains zinc sulphite and a protective oxide selected from the group consisting of aluminum and iron oxides together with a copper fungicide and an arsenical insecticide.

ALEXANDER A. NIKITIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,626,872 Piver May 3, 192,7 1,905,532 Vannah Apr. 25, 1933 2,051,910 Sessions Aug. 25, 1936 2,368,565 Pearce et al Jan. 30, 1945 2,376,740 Water et al. May 22, 1945 

1. A COMPOSITION FOR APPLICATION TO PLANT FOLIAGE AND FRUIT FOR THE CONTROL OF PESTS WHICH CONTAINS ZINC SULPHITE TOGETHER WITH COPPER FUNGICIDE. 